1. Field of the Invention
The present invention relates to a tape loading apparatus for use in a magnetic recording/reproduction apparatus, such as a video tape recorder (VTR).
2. Description of the Related Art
Recently, recording density has increased as magnetic recording/reproduction apparatuses, such as VTRs, etc., have become digital and miniaturized. As a result, there is a demand for an improved precision tape running system. Of course, a high degree of precision is required for a tape loading apparatus. For audiovisual products, there is a trend toward reduced size and cost. The same is true of magnetic recording/reproduction apparatuses, such as VTRs, etc.
A conventional tape loading apparatus will be described below. For example, Japanese Patent No. 2701575 discloses a conventional tape loading apparatus. FIGS. 5, 6 and 7A through 7D illustrate this conventional tape loading apparatus for use in a VTR. These figures are based on FIG. 3, 4, 5 and 15 of Japanese Patent No. 2701575. FIGS. 8 and 9 illustrates a tape guide post mechanism for a conventional tape loading apparatus, such figures being based on FIGS. 4 and 5 of Japanese Patent No. 2789838, respectively. For sake of simplicity, the xe2x80x9cboat reference surfacexe2x80x9d and xe2x80x9creference surfacexe2x80x9d referred to in Japanese Patent No. 2701575 with respect to FIG. 15, are referred to differently herein as the xe2x80x9cboat-side reference surfacexe2x80x9d and xe2x80x9cbase-side reference surfacexe2x80x9d in relation to FIG. 7.
In FIG. 5, reference numeral 52 indicates a cassette, 63 indicates a magnetic tape, and 69 indicates a rotary head cylinder. Reference numeral 58 indicates a feed side loading roller post serving as a tape guide post, which guides the running of the magnetic tape 63. Reference numeral 64 indicates a feed side boat serving as a carrier which carries the feed side loading roller post 58 and an inclined post 66, and draws the magnetic tape 63 present within the cassette 52. Other than these tape guide posts, a plurality of tape guide posts (representing a tape guide post group), such as a tension post 59, take-up side loading posts 60 and 61, and an auxiliary guide post 73 are also used to withdraw the magnetic tape 63 present within the cassette 52. Therefore, a predetermined tape running system is established, so that sound or visual images can be recorded to or reproduced from the magnetic tape 63.
Referring to FIGS. 5 and 6, the magnetic tape 63 withdrawn out of the feed side reel 53 is wrapped about the feed side loading roller post 58 via tape guide posts 59, 76 and 66. Thereafter, the magnetic tape 63 is wrapped about the rotary head cylinder 69, and then about the take-up side loading post 60. The magnetic tape 63 reaches a take-up side reel 54 via a predetermined tape running system. FIG. 6 is a perspective view showing only parts which are associated with the tape running system in the state shown in FIG. 5.
Referring to FIGS. 7A to 7D, reference numeral 51 indicates a chassis as a base, 86 indicates a stopper, 53 indicates a drive shaft. Three boat-side reference surfaces are provided on the rear side of the feed side boat 64. FIGS. 8 and 9 are diagrams showing the mechanism of the tape guide posts and their vicinity of the conventional tape loading apparatus. The arrangement shown in FIGS. 8 and 9 is a typical mechanism of adjusting the height of conventional tape guide posts.
In FIGS. 8 and 9, reference numeral 65 indicates a take-up side boat serving as a carrier, 68 indicates a pipe having an internal thread portion 68a and cylinder portion 68b, which is press-fit onto the take-up side boat 65. Reference numeral 60 indicates a take-up side loading post comprising a roller 60a, a shaft 66, a roller holding member 67, and an upper flange 60b. The roller holding member 67 and the upper flange 60b are press-fit onto the shaft 66. The roller 60a is rotatably supported at an upper portion 66a of the shaft 66 while the upper limit of the position of the roller 60a is defined by the upper flange 60b and the lower limit of the position of the roller 60a is defined by the roller holding member 67. The upper flange 60b and the roller holding member 67 also keep the running of the magnetic tape within the upper and lower limits. The roller holding member 67 has an external thread portion 67a, which engages the internal thread portion 68a of the pipe 68. Reference numeral 80 is a screw which engages an internal thread portion provided in a screw hole 81 of the pipe 68. The tip of the screw 80 presses the circumferential surface of a lower portion 66b of the shaft 66. A hexagonal hollow or slot portion is provided on the top portion of the upper flange 60b, which is engaged with a tool, such as a driver etc., to rotate the upper flange 60b. The rotation of the upper flange 60b causes the shaft 66 and the roller holding member 67 to rotate together.
It should be noted that although the upper flange 60b, the roller 60a, the external thread portion 67a, the internal thread portion 68a, the cylinder portion 68b, the upper portion 66a, and the lower portion 66b are not designated in FIG. 5 of Japanese Patent No. 2789838, these names are added in FIG. 9 for the sake of clarification and convenience. Japanese Patent No. 2701575 does not describe the mechanism of adjusting the height of a tape guide post in the loading mechanism. In fact, the height adjusting mechanism as shown in FIG. 5 of Japanese Patent No. 2789838 is generally incorporated into the loading mechanism. Hereinafter, it is assumed that the height adjusting mechanism as shown in FIG. 5 of Japanese Patent No. 2789838 is incorporated into the loading mechanism of Japanese Patent No. 2701575.
The operation of the thus-constructed conventional tape loading apparatus will be described. The feed side boat 64 is in a state shown in FIGS. 7A and 7B when the loading operation has been completed. Specifically, the drive shaft 53 biases the feed side boat 64 to the left. This biasing force causes the feed side boat 64 to contact and press the stopper 86. The feed side boat 64 experiences a reaction force from the stopper 86 in a direction indicated by arrow F (FIG. 7D). As a result, the three boat-side reference surfaces on the rear side of the feed side boat 64 are caused to press the base-side reference surface of the chassis 51, so that the feed side boat 64 is tightly fitted with the base-side reference surface. Therefore, the height of the feed side boat 64 is determined with a high degree of precision only after the feed side boat 64 is in such a state. In this case, the inclination of the feed side boat 64 is also determined with a high degree of precision. As a result, the height and inclination of the feed side loading roller post 58 (tape guide post) carried by the feed side boat 64 are determined with a high degree of precision.
For the current VTR, the width of a track recorded in a magnetic tape is 5 to 20 xcexcm. Therefore, a magnetic tape wrapped about a rotary head cylinder requires a precision of 1 to 2 xcexcm with respect to their relative positions. Therefore, the height precision and inclination of a tape guide post placed near the rotary head cylinder are very important. Specifically, referring to FIG. 6, the precision of the position and inclination of the feed side loading roller post 58 and the take-up side loading roller post 60 is particularly important. The height and inclination of these tape guide posts require a precision of several xcexcm and about 0.2xc2x0 to 0.5xc2x0, respectively. In the future, a higher degree of precision is required as recording density is increased. Needless to say, the greater the height and inclination precisions, the better the quality.
In FIGS. 7A to 7D, variations in the height of the base-side reference surfaces and the height of the feed side loading roller post 58 with respect to the feed side boat 64 are about 10 to 50 xcexcm. Therefore, it is difficult to guarantee a height precision of several xcexcm by simply assembling parts. To avoid this difficulty, in the arrangement shown in FIGS. 8 and 9, for example, the height of the tape guide post 60 is adjusted to obtain required precision by rotating the tape guide post 60, with the hollow portion of the upper flange 60b of the tape guide post 60 being engaged and rotated by a driver.
In order to maintain the precision after the height adjustment, there must not be a play in the vertical direction between the external thread portion 67a of the roller holding member 67 and the internal thread portion 68a of the pipe 68 when they are engaged with each other in FIG. 9. The height of the tape guide posts must not be changed due to vibration, repetition of use, aging, etc. In the arrangement shown in FIG. 9, the screw 80 is laterally driven to press the lower portion 66b of the shaft 66 against the internal wall surface of the cylinder portion 68b of the pipe 68, so that the tape guide post 60 is secured to a carrier (in this case, the take-up side boat 65). Therefore, the height of the tape guide post 60 is prevented from being deviated from the adjusted state.
Referring again to FIG. 7B, the precision of the inclination of the tape guide post 58 is the sum of the inclination precision of the base reference surfaces and the inclination precision of the tape guide post 58 with respect to the boat-side reference surfaces. Therefore, in order to ensure the above-described inclination precision of 0.2xc2x0 to 0.5xc2x0, the inclination precision of the base-side reference surface is about 0.1xc2x0 to 0.3xc2x0 and the inclination precision of the tape guide post 58 with respect to the boat-side reference surface is about 0.1xc2x0 to 0.3xc2x0, which is a typical specification for this arrangement. Therefore, typically, the cylindricity of the internal wall surface of the cylinder portion 68b (FIG. 9) of the pipe 68 is about 1 to 3 xcexcm, and the inclination precision of the cylinder portion 68b with respect to the boat-side reference surface is about 0.1xc2x0 to 0.3xc2x0.
There are, however, the following problems with the above-described conventional arrangement. Variations in the inclination of a tape guide post with respect to a base is basically the sum of variations of the inclination of a base-side reference surface and variations in the inclination of the tape guide post with respect to the boat reference surface. High precision machining is required for the base reference surface and the cylinder portion of a pipe with respect to the boat reference surface. Such high precision requires the state of the art machining technology, which leads to an increase in cost for parts. The term xe2x80x9cmachiningxe2x80x9d as used herein refers to industrial machining, such as cutting, alloy sintering, resin molding, etc.
The supporting portion of the tape guide post 60 (the lower portion 66b of the shaft 66 in the arrangement shown in FIG. 9) needs to be disposed along the internal wall surface of the cylinder portion 68b of the pipe 68 with a high degree of precision. From this reason, the length of the engagement of the pipe 68 and the tape guide post 60 cannot be smaller than a predetermined size. Therefore, a problem arises in miniaturization.
The carriers 64 and 65 must be made of a material capable of being generally machined with a high degree of precision, such as cast metals (e.g., zinc die-cast or aluminum die-cast) or super engineering plastics (e.g., PPS, etc.), leading to problems such as the costs for materials for parts and molding the materials are high.
In the arrangement of FIG. 7, there is substantially no means for adjusting the inclination of the tape guide post 58 after assembly. Parts having insufficient inclination precision are abandoned, resulting in low yield and high cost.
The carrier and the tape guide post are not perfectly rigid bodies. Even if there is no play in the engagement between the carrier and the tape guide post, the tension of a magnetic tape causes slight elastic deformation of the carrier and the tape guide post. Therefore, fluctuation of tape tension slightly modifies the inclination and height of a tape guide post, whereby the inclination and height of the tape guide post become unstable.
When a carrier is made of zinc die-cast or resin which is easy to shape, the carrier is slightly deformed over time, particularly under high temperature. In this case, the inclination and height of a tape guide post is slightly changed, thereby reducing the inclination and height precisions of the tape guide post. A thicker carrier is required in order to minimize such variations, but the larger size inhibits miniaturization.
When the height of the tape guide post is adjusted with respect to the carrier, the following problem arises. The lower portion of the tape guide post supported by the carrier cannot be produced in such a manner as to be perfectly parallel to the tape guide portion of the tape guide post. It is impossible to manufacture a tape guide post such that the lower portion of the tape guide post supported by a carrier is perfectly in parallel to the tape guide portion of the tape guide post. Specifically, in FIG. 9, the lower portion 66b and the upper portion 66a of the shaft 66 are not perfectly in a straight line. Therefore, the roller 60a supported by the upper portion 66a cannot be manufactured to be perfectly in parallel to the lower portion 66b. Therefore, when a tape guide post is rotated in adjusting the height of the tape guide post, such a slight angle difference causes the tape guide portion to be precessed with respect to the carrier. Therefore, the height adjustment changes the inclination of the tape guide portion with respect to the base, thereby reducing the inclination precision of the tape guide post.
According to one aspect of the present invention, a tape loading apparatus comprises a base, a tape guide post for guiding running of a tape, a carrier for carrying the tape guide post and conveying the tape for tape loading, a post engagement member provided on the base for fixing the position in the plane of an end portion of the tape guide post by being engaged with the end portion of the tape guide post, and an inclination adjusting portion for continuously and variably shifting the post engagement member in the plane to adjust the inclination of the tape guidepost. Therefore, the position in the plane of an end of the tape guide post is directly fixed by the post engagement member, thereby determining the inclination of the tape guide post. The inclination precision of the tape guide post with respect to the carrier is independent of the inclination precision of the tape guide post with respect to the base. The inclination precision of the tape guide post with respect to the carrier can be greatly relaxed, whereby high-precision machining is not required for the base and therefore cost can be reduced.
There is no need for a base-side reference surface for determining the inclination of the carrier and thus high-precision machining of the base-side reference surface is not required, thereby making it possible to reduce cost. The portion supporting the tape guide post need not be provided along the engagement portion of the carrier (the internal wall surface of the cylindrical portion of the pipe in the conventional example). The length of the engagement between the carrier and the tape guide post can be small, resulting in easy miniaturization.
The relaxed precision requirements leads to a reduction in space of the engagement between the carrier and the tape guide post. Specifically, in the example, the length of the hole portion 2i of the boat 2 (length in the direction of arrow H) can be small, whereby miniaturization can be easily achieved.
Further, by shifting the post engagement member in the plane, the inclination of the tape guide post can be continuously adjusted, whereby the tape guide post can approach a predetermined inclination with a high degree of precision.
In one embodiment of thin invention, the inclination adjusting portion is configured so that the relative position between the post engagement member and the base is continuously and variably adjusted with a screw mechanism the relative position between the post engagement member and the base can be finely adjusted with a simple structure and simple procedures. The inclination of the tape guide post can be adjusted with a high degree of precision with low cost and small space.
In one embodiment of thin invention, the inclination adjusting portion comprises an internal thread portion provided on the base, a hole provided in the post engagement member for fixing the position in the plane of the tape guide post, and an inclination adjusting screw passing through the hole and engaging the internal thread portion. Therefore, the inclination of the tape guide post can be adjusted with great precision by the above-described simple structure with low cost, i.e., the formation of the hole and the internal thread portion and the addition of the inclination adjusting screw.
In one embodiment of this invention, a V-shaped cut for fixing the position in the plane of the tape guide post is provided in the post engagement member, and the cut is engaged with the end portion of the tape guide post. With the V-shaped cut, the position of the portion of the tape guide post can be determined with a higher degree of precision. Therefore, the reproducibility of the inclination of the tape guide post is excellent, whereby the inclination precision of the tape guide post can be further improved.
Thus, the invention described herein makes possible the advantages of providing a tape loading apparatus such that cost can be reduced and miniaturization is easy while the precision which is as well as or better than conventional tape loading apparatuses.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.